July 2015

Breaking: CryoSat ice data now open to all!

I figured this would be worth de-hibernating for (hat-tip Gas Glo). From the ESA homepage:

1 February 2011

Scientists can now tap into a flow of new data that will help to determine exactly how Earth's ice is changing. This information from ESA's CryoSat mission is set to make a step change in our understanding of the complex relationship between ice and climate.

Considering the loss of the original CryoSat satellite during launch in 2005, scientists around the world have had a long wait for information on ice thickness – making the release even more of a milestone for the mission.

ESA's CryoSat Mission Manager Tommaso Parrinello announced the release at the CryoSat Validation workshop currently taking place. He said, "We are pleased to announce this important milestone, which comes only few weeks after the end of the commissioning phase.

"As of today, the international science community will have free and easy access to all of the measurements from CryoSat. This will amount to a unique dataset to determine the impact climate change is having on Earth's ice fields."

CryoSat's polar orbit reaches latitudes of 88°. This orbit brings it closer to the poles than previous Earth observation satellites, covering an additional 4.6 million sq km – an area larger than all 27 European Union member states put together.

This TOPAZ3 image is merely based on data assimilation and ocean general circulation model predictions, like PIOMAS (made at the Mohn-Sverdrup Center
Global Ocean Studies - Operational Oceanography, in Norway). Note the scale at right is from 0 meters to 3 meters thick. The date Sep 19, 2010 is the day of minimum ice extent last summer (Northern hemisphere).

Using this average monthly volume, the average height of the Arctic ice was 0.87 meters last Sep 19. Since the volume that day was almost certainly less than the monthly average, the average ice height on Sep 19 was even lower.

It would be nice if some institution publicly serving up CryoSat-2 data (NSIDC? ESA?) would include the average height, and volume, of the Arctic ice each day of the spring/summer season. On the PIOMAS charts, an anomaly of -13.5 on the minimum extent day of the summer melt season corresponds to ICE GONE. We'll soon see (next three years) if Maslowski's high resolution Arctic ocean models were essentially correct.

Hiya, Anu, good to see you pop in. I'm also very curious to see if and how CryoSat-2 data will be added to the arsenal this melting season. Does anyone have any idea what's going to happen? Should I go and bother some cryospheric scientists? I'm still hibernating, you know. ;-)

Did you know that you can download the data behind the Topaz images from the following URL (but let's be kind to their server and not all download it all at once, as it is over 4 GB -- if anyone knows a place I can put it, let me know and perhaps I could set up a mirror for those of us you are interested):

I have calculated extent, area, and volume based on that data (which doesn't including the bering strait, so it is a bit hard for me to verify, but I'm planning to break the data out by "cryosphere today regions" soon). Here are the model's values for high and low:

I notice that the max volume is reached much later than the max extent/area (I assume this is because, during spring, the central ice continues to thicken while the marginal ice is slowly melting). Also notice that volume is about 10% lower than this time last year. (And volume in general is falling about 10% per year).

Bfraser, that looks very interesting, thanks. We can always turn one of those posts into a full blog post if you'd like. I'm sure a lot of people would be interested in more info on Topaz (I know I would).

BTW, why do TOPAZ and PIPS differ so much? PIPS has 4-5 meter ice to the North of Greenland (in the Lincoln Sea, etc), whereas TOPAZ has all the thick (3 meter) ice at the entrances of the Canadian Archipelago.

Obviously, these 2 systems use different data and algorithmins and are off by a few days.
Beyond that I can do is offer a guess that there were atmospheric conditions that threw 1 of these systems off. Also, PIPS does show some thick ice near Prince Patrick Island.

Anu, Maslowski's projection (for *mostly* ice-free conditions, this to account for remnant ice that is expected to persist in the Nares Starit region after the main pack is gone) is for 2016 +/- 3 years, so a melt-out as late as 2019 would still validate. Also bear in mind that at first the ice-free period is likely to be quite brief.

That said, I'm really wondering if the polar vortex will be able to re-form at all under such conditions. If it can't I think we're talking a new and possibly persistent climate regime for the Arctic, one with implications for abrupt change gloablly. I hope I'm wrong.

Shifting gears a little, I just noticed this new paper detailing the Holocene histroy of Jakobshavn Isbrae. The upshot: "The ice margin near Jakobshavn thus underwent large and rapid adjustments in response to relatively modest centennial-scale Holocene temperature changes, which may foreshadow GIS response to future warming." (I'm reminded of Hansen's comment to the effect that the apparent relative stability of the ice sheets during the Holocene -- a result of the slight tapering off of orbital forcing since Holocene peak warmth -- could have been Nature's way of tricking us into a false sense of security.) Mauri, if you're reading this could you perhaps provide some interpretation?

"geological data suggest that both marine- and land-terminating margins of the western GIS will likely undergo significant and prolonged retreat if future temperatures match those reached during the middle Holocene."

Given the above, it bears keeping in mind this statement from page 14 of Hansen 2011:

"Earth today, with global temperature having returned to at least the Holocene maximum, is poised to experience strong amplifying polar feedbacks in response to even modest additional global mean warming."

Daniel, that Hansen 2011 paper is just plain scary, and in very plain English. It's a real shame that there is so little interest in these things in the blogosphere. The long term temperature graphs are very interesting and show all sorts of changes.

It's true Maslowski's projection is for "mostly ice free" by 2016 ± 3 years, but that is for ON (October/November) Fall Arctic conditions, as mentioned in this presentation (page 12 out of 13). The minimum summer Arctic ice volume is consistently 2,500 to 5,000 km^3 less than this ON value. This fact, plus the linear volume trend of -1075 km^3 per year even for the ON values, makes me suspect a largely ice free summer minimum within four years, even if the Arctic Fall is not "mostly ice free" until 2019.

Assuming that Cryosat-2 data validates the PIOMAS model, approximately (it was validated pretty well with ICESat data a few years back - in fact, PIOMAS had higher volume than the ICESat data in November of 2007), then last summer the Arctic summer minimum was less than 4000 km^3 (4000 was the average for the month of September), so we could see this minimum drop by 1000 km^3 this summer. Given that the average thickness was about 81.6 cm for last September (avg extent 4.9 million km^2, avg volume 4000 km^3) - perhaps 80 cm on the thinnest day of the summer - then we might see the thinnest day drop to 60 cm for this September, with extent about the same. Then 40 cm next summer (same extent), then 20 cm (same extent), then gone.

But I doubt the extent will stay roughly the same as the Arctic ice gets thinner and thinner. The margins will disappear, and large rifts might open up, leaving large "ice islands". I expect we will be seeing some pretty amazing things in the next four Arctic summers.

I am not sure that "And volume in general is falling about 10% per year" does it justice. I would be more inclined to say approx 1m fall in minimum volume p.a. With 4.3m left at last minimum that seems about 4 years.

However even that doesn't seem to reflect things:

Based on volume currently being 1.37m below last year, the max volume this year could well be 16.6m or less. The reductions in volume from max to min over the last four years have been:
16.8m, 17.2m, 13.8m and 13.6m

So it seems you could say that the maximum volume this year could well be less than the volume reduction in 2 of the last 4 years! ouch!

I was expecting an upward trend in both volume reduction and in volume increase. If the upward trend is right then there is a high probability of very low ice this year. However, perhaps there is a downward trend in volume reduction because I wasn't realising there is a big issue of extra heat from albedo change not being in places where it can melt ice.

The PIOMAS min volume figures are not wildly different from the ones Bfraser reports. But the max volumes are quite different - for April 2010, still over 20,000. TOPAZ numbers would show an even more rapid volume decrease in max volume than the fairly gloomy PIOMAS numbers we've been interrupting Neven's naps with over the last few months. PIOMAS gives us a 10% decline in max volume over the last four years. Bfraser's figures show a 25% decline.

The linear trend in PIOMAS volume reductions is +343pa and the linear trend in the volume increase is +381pa. If these linear trends presist, they will reduces the amount by which the minimum falls each year but by a mere 38. This is negligable compared to the average difference between volume reduction and increase of about 1000 for 2011.

2014 +/-3 years would seem to be the estimate based on linear trends in volume reduction and volume increase per last 5 years of PIOMAS data persisting. Note 5 years is very short particularly if there could be a decadal oscilation.

It might take a while before we can expect useful data. I've asked around and was told it might take at least year for the phase of calibration etc to end. So unfortunately it looks as though CryoSat won't be a helpful resource this melting season. Hopefully the next one.

The world is going to be shocked when some time this decade the Arctic Ocean completely melts away during the summer. It's going to feel like we are living on an alien planet, to look at the MODIS or cryosphere today imagery and see one vast ocean there. It's going to creep a lot of people out, and it may just be the thing to finally discredit the AGW-deniers and get people serious about AGW.

Not to mention, we might witness totally different weather patterns setting up in the late fall due to delayed re-freezing and latent heat warming the arctic coasts. We might get a really weird situation where Pevek, Russia and Barrow, Alaska enjoy balmy ~0-degree Celsius temperatures well into November as latent heat from the open ocean and the arctic re-freezing maintain temperatures around freezing (in effect benefiting for the first time in human history from a maritime climate), while points from Yellowknife to Edmonton get left a continental climate that is colder, despite being farther south.

We are already seeing how relatively balmy Greenland has been thanks partly to the ice on the western coast not making it down very far south. I predict, that, if you are into real estate, that the maritime arctic is where you might want to be looking these next ten years.

Last year, sea ice extent went from near record lows near February to an apparent recovery mid April only to recede between then and September to near records lows again. The thinking was that the pack was so thin and rotten last winter that sea ice was much more free to move about and that the April "recovery" was totally deceptive as it was reflective of the mobility of the ice as opposed to a true extent.

So, are we in for more of the same?

There is little reason to suspect that sea ice is currently any thicker or more robust than last year and we are nearing the spring season.

I don't think the April recovery was deceptive. Slight, but real. If it was just spreading, then the area should have increased more than the volume at this time (ie average thickness should have dropped, relatively). I suspect area to extent should also have dropped, but I don't have data for that window; my IJIS area:extent data only covers April to October, but Lodger's CAPIE figures might shed some light.

When you compare April to January, you find that although all the numbers (extent / volume / thickness) are headed south, March, April and May are all increasing in thickness relative to January. Thirty years ago, these months were 6%, 14% and 24% thicker than January. More recently they have been 13%, 23% and 33% thicker. The trend for these months is about +0.27 percentage points per year - ie the ratio has been growing by about 1% every three or four years. Note - there was a big jump in these figures in 2004, and we see a lower rate of change either side of that jump.

Thickness is dominated by the amount of thin first year ice. Thickness peaks in summer, because the new thin ice melts leaving a core of old thick ice. It is near minimum in December after the rapid growth of new ice. Due to the later freeze from a lower minimum, this growth is now extending into January and those figures have been dropping more quickly than April, where all the numbers have been a bit more stable.

I agree that often extent growth is really just spreading, and is bad overall, in this case, I think the pack was genuinely putting on weight in April, and this was pretty much the only thing that saved 2010 recording the lowest ever extent.

Your question supposes that the state of the pack in April was possibly very bad, and you ask whether it will be equally bad this year. But I think it would be more accurate to suppose that the pack was in notably good condition (all things considered), and ask whether we will get such good conditions in March-April this year.

As Kylie Minogue put it: "I should be so lucky..."

We'll know soon. We are just at the point at which 2006 and 2007 diverged from 2010, with the former flatlining towards historically low maxima, and the latter putting on some late season weight. Interesting times....

Take for example, the coast of labrador. This was ice free until Mid January. There is now considerable ice off the Labrador coast, however it is all grey or grey-white ice, which means it is less than a foot thick. It may make it to thin first year ice by the time the melt season starts, but this will quickly melt out.

This may lead to a new intereting observation. As the lower total maximun ice extent pushes the ice farther north. It pushes the date of the maximun ice extent latter also.

Normally the maximun extent is in early March, but this is base on ice that has pushed a lot further south. Now with the ice edge farther north, there are a few more weeks of cold weather to support ice growth along the ice edge, and thus a latter maximun extent.

However the ice is much thinner, and when the melting starts, we see a greater rate of loss. I think we are going to see 2010 repeated for many years to come, with delayed maximun extents, followed by greater loss in the early spring.

► Besides the underlying 0.02° C warming every year since 2007 (0.2° C/decade these days), which makes the ocean heat transported to the Arctic larger every summer (most likely), the sunspots are starting up again:http://spaceweather.com/
Today there are 84.
Late summer 2007 was during the low point in a cycle:http://sidc.oma.be/html/wolfmms.html

► And of course, Cryosat-2 data about the volume of the Arctic ice in late September will leak out - even if there is no "official" site like NSIDC presenting the data in a public-friendly manner, the fact that so many organizations all over the world have access to this data seems to guarantee that somebody will get at least a rough draft out to Arctic watchers. I expect volume to be much lower than 4000 km^3 at September's minimum.

Careful with this one. There is probably a delay in the region of 6 to 10 months before effects reach arctic so we are only just beginning to get effects of La Nina that started about 7 months ago and these effects can be expected to last for at least 7 months so we will only get La Nina effects during the coming melt season.

"the sunspots are starting up again"
True as far as direct sunlight on ice is concerned. However, consider albedo, if the main effect is on water that reaches arctic this year but has been travelling there over last few years, the sunspot numbers for the last three years is considerably lower than for the three years before that.

Great discussion, guys. I'm still not sure what the effect of ENSO is on the Arctic sea ice. Wayne Davidson had a very interesting theory, but it didn't play out exactly like he thought it would last melting season.

BTW, here is Open Thread 6, most likely the last open thread for the growing season.

I'm also very vague about what effect he ENSO cycle has on the Arctic Sea ice.

I have been particularly looking for anything that indicates whether La Nina/El Nino would push Northern Pacific water into the Arctic, or pull Arctic Ocean water into the North Pacific. But I can find very little online that discusses ENSO and the Arctic Sea Ice at all.

Idunno, also interesting (and just as elusive) is a possible effect of ENSO on cloud formation in the Arctic. You can read the piece I wrote on Wayne Davidson's anvil seeding theory here: Arctic sea ice melt: a correlation with ENSO?

I had a very quick look at ENSO index for the last 30 years and compared to CT area. If there is any correlation it seems quite weak, but that's just eyeballing it.

I thought about delay between ENSO changes and melting changes and noticed one thing: to the naked eye, the strongest correlation appears to be with about a one year offset, but with ice melt changes leading ENSO changes by 12-24 months

Crazy idea I know, but maybe Arctic ice melt affects El Nino, rather than the other way around...
(Just putting it out there - personally, I don't really see much of a correlation at all).

ENSO -> Arctic ice melt? I suspect that the 'advance' melting is just another indicator that the oceans are the biggest reservoir of heat. Maybe the first, previously imperceptible, signal of heat releasing from the ocean for an El Nino event begins in the northern rather than the southern Pacific.

Rather like bending the knees for take-off before taking a big jump. We're like novices watching athletic events. We see the height and distance travelled. A more knowing coach or competitor would watch actions and behaviours long before we even notice any movement.

La Nina effects are mainly expressed as increased sea ice concentration in the Sea of Okhotsk and Bering Sea. This year, both are low/normal. The obvious conclusion is this year's La Nina is very small relative to background warming.

If the sunspot numbers shoot up this year:http://sidc.oma.be/html/wolfmms.html
this will be another small forcing added to the underlying ocean warming. And it will only get worse in summer 2012 - if Cryosat-2 confirms PIOMAS, these might be the last few Arctic summers that don't have some time essentially ice-free.

Will the CROSAT data be sufficiently sensitive to detect these small differences as the ice sheet breaks up into a fractured patchwork of ice that floats atop swells from Arctic storms, winds and tides?

CROSAT may be useful in measuring the thickness of land fast ice, but we may be asking too much of it if we are expecting it to chart a neat map of ice thickness for floating sea ice.

How will the data be adjusted for the rise in sea level from global warming?

How will ithe Crysat 2 data overcome tides and wave actions to provide meaningful measurement of changes in height of floating sea ice?

At least with Terra and Aqua we can "see" the ice cover on a daily basis.

@William Crump: Will the CROSAT data be sufficiently sensitive to detect these small differences as the ice sheet breaks up into a fractured patchwork of ice that floats atop swells from Arctic storms, winds and tides?

Hi Will,

The ESA CryoSat website says: "CryoSat carries a sophisticated radar altimeter that can measure the thickness of sea ice down to centimetres and detect changes in ice sheets, particularly around the edges where icebergs are calved from the vast ice sheets that cover Greenland and Antarctica."

It's main instrument (SIRAL) operates in three modes:
A standard radar altimeter for use over open oceans and ice sheets. I think you are right to doubt the precision of this, but for CryoSat's purposes that is not a huge problem. It will be able to be correct for tides, storms etc over the ocean to a "fairly good" level.
A synthetic aperture radar for use over sea ice, which combines signals "in post" to provide greater resolution than the standard mode, particularly for mapping leads and smaller floes.
This SAR plus signals from a second antenna combined using interferometry to achieve an accuracy of 1 cm (according to the SIRAL project manager Laurent Rey) in looking in very close detail at "varied" terrain - glacier snouts, the interface between land and fast ice etc.

I doubt they can get cm accuracy over the whole basin (it gathers data in 250 m swaths, which would be a truckload of data), but presumably, the three different levels of accuracy can be combined to give a highly accurate picture - certainly good enough to tell whether the ice is 1 m thick or 50 cms thick.

Not sure about the other issues you raise - I suggest a visit to the ESA site; they have quite a bit of info, since they are justifiably proud of their new baby. Even if it fails to meet the standards you lay out, it is far and away the most accurate instrument we've ever had for this purpose.

I think it's more like 1/8 of the ice floats above sea level:http://news.bbc.co.uk/2/hi/science/nature/8615172.stm
But you are right, they are measuring the freeboard (ice above the waterline), so the expected accuracy of ± 2.5 cm in measuring this freeboard translates into an accuracy of ± 20 cm in total ice thickness.

I guess that's pretty significant along the margins in the summer, when they might measure ice 40 cm thick - it could actually be 20 to 60 cm thick.

http://www.the-cryosphere-discuss.net/4/641/2010/tcd-4-641-2010.pdf
(They are looking into ways to average over a large number of measurements with Cryosat, to get the freeboard uncertainty down to ± 1.0 cm. I wouldn't be surprised if the data processing improved over the life of the mission). Also, ice of different density has slightly different percentages of freeboard - they are looking into that too, always looking for maximum accuracy.

Will the CROSAT data be sufficiently sensitive to detect these small differences as the ice sheet breaks up into a fractured patchwork of ice that floats atop swells from Arctic storms, winds and tides?
Actually, they need to compare the radar signal from the water surface and the top of the freeboard surface, so a "fractured patchwork of ice" is perfect for this instrument. The problem is in the winter, where they need open water in a a narrow crack ("lead") to get the water height to compare to:http://www.redorbit.com/news/space/1829162/cryosat_mission_scientist_interview_with_mark_drinkwater/
(interview with ESA’s Mission Scientist for CryoSat, Mark Drinkwater)

How will the data be adjusted for the rise in sea level from global warming?
How will ithe Crysat 2 data overcome tides and wave actions to provide meaningful measurement of changes in height of floating sea ice?
It's a 3.5 year mission - sea level rise is glacial.
Tides are likewise very slow - the SIRAL radar has 50 microsecond pulses. I'm sure they can handle waves, too - except maybe crashing waves on some Siberian beach - I'm not sure how the new less-ice Arctic is affecting beach action in Septembers.